A powerful double radio relic system discovered in PSZ1 G108.18-11.53: evidence for a shock with non-uniform Mach number?

Gasperin, F. de; Intema, H. T.; Weeren, R. J. van; Dawson, William A.; Golovich, Nathan; Wittman, David; Bonafede, A.; Brüggen, M.

doi:10.1093/mnras/stv1873

Cited by 47 publications

(41 citation statements)

References 63 publications

(91 reference statements)

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“…The SPAM software (including the pipeline) can be obtained through . The SPAM pipeline has been successfully applied in many scientific investigations that make use of GMRT observations in any of the observing bands below 1 GHz, (150, 235, 325, and 610 MHz;e.g., van Weeren et al 2014a,b;Wykes et al 2014;Bonafede et al 2014Bonafede et al , 2015de Gasperin et al 2014de Gasperin et al , 2015.…”

Section: Appendix A: Spam Pipelinementioning

confidence: 99%

The GMRT 150 MHz all-sky radio survey

Intema

Jagannathan

Mooley

et al. 2017

A&A

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836

767

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We present the first full release of a survey of the 150 MHz radio sky, observed with the Giant Metrewave Radio Telescope (GMRT) between April 2010 and March 2012 as part of the TIFR GMRT Sky Survey (TGSS) project. Aimed at producing a reliable compact source survey, our automated data reduction pipeline efficiently processed more than 2000 h of observations with minimal human interaction. Through application of innovative techniques such as image-based flagging, direction-dependent calibration of ionospheric phase errors, correcting for systematic offsets in antenna pointing, and improving the primary beam model, we created good quality images for over 95 percent of the 5336 pointings. Our data release covers 36 900 deg 2 (or 3.6 π steradians) of the sky between −53• and +90• declination (Dec), which is 90 percent of the total sky. The majority of pointing images have a noise level below 5 mJy beamwith an approximate resolution of 25 × 25 (or 25 × 25 /cos (Dec − 19 • ) for pointings south of 19 • declination). We have produced a catalog of 0.62 Million radio sources derived from an initial, high reliability source extraction at the seven sigma level. For the bulk of the survey, the measured overall astrometric accuracy is better than two arcseconds in right ascension and declination, while the flux density accuracy is estimated at approximately ten percent. Within the scope of the TGSS alternative data release (TGSS ADR) project, the source catalog, as well as 5336 mosaic images (5• × 5 • ) and an image cutout service, are made publicly available at the CDS as a service to the astronomical community. Next to enabling a wide range of different scientific investigations, we anticipate that these survey products will provide a solid reference for various new low-frequency radio aperture array telescopes (LOFAR, LWA, MWA, SKA-low), and can play an important role in characterizing the epoch-of-reionisation (EoR) foreground. The TGSS ADR project aims at continuously improving the quality of the survey data products. Near-future improvements include replacement of bright source snapshot images with archival targeted observations, using new observations to fill the holes in sky coverage and replace very poor quality observational data, and an improved flux calibration strategy for less severely affected observational data.

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Section: Appendix A: Spam Pipelinementioning

confidence: 99%

The GMRT 150 MHz all-sky radio survey

Intema

Jagannathan

Mooley

et al. 2017

A&A

Self Cite

836

767

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“…A: Kocevski et al (2007), Stroe et al (2013), van Weeren et al (2010) a very high polarization fraction above 50% (Bonafede et al 2009;van Weeren et al 2010van Weeren et al , 2011cvan Weeren et al , 2012Kale et al 2012;Lindner et al 2014;de Gasperin et al 2015). The high degree of polarization could originate from a large-scale regular magnetic field or from the compression of a small-scale tangled field in the shock front, which aligns the magnetic field lines along the structure of the shock (Laing 1980).…”

Section: Introductionmentioning

confidence: 99%

Relics in galaxy clusters at high radio frequencies

Kierdorf

Beck

Hoeft

et al. 2017

A&A

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110

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Aims. We investigated the magnetic properties of radio relics located at the peripheries of galaxy clusters at high radio frequencies, where the emission is expected to be free of Faraday depolarization. The degree of polarization is a measure of the magnetic field compression and, hence, the Mach number. Polarization observations can also be used to confirm relic candidates. Methods. We observed three radio relics in galaxy clusters and one radio relic candidate at 4.85 and 8.35 GHz in total emission and linearly polarized emission with the Effelsberg 100-m telescope. In addition, we observed one radio relic candidate in X-rays with the Chandra telescope. We derived maps of polarization angle, polarization degree, and Faraday rotation measures. Results. The radio spectra of the integrated emission below 8.35 GHz can be well fitted by single power laws for all four relics. The flat spectra (spectral indices of 0.9 and 1.0) for the so-called Sausage relic in cluster CIZA J2242+53 and the so-called Toothbrush relic in cluster 1RXS 06+42 indicate that models describing the origin of relics have to include effects beyond the assumptions of diffuse shock acceleration. The spectra of the radio relics in ZwCl 0008+52 and in Abell 1612 are steep, as expected from weak shocks (Mach number ≈2.4). Polarization observations of radio relics offer a method of measuring the strength and geometry of the shock front. We find polarization degrees of more than 50% in the two prominent Mpc-sized radio relics, the Sausage and the Toothbrush, which are among the highest percentages of linear polarization detected in any extragalactic radio source to date. This is remarkable because the large beam size of the Effelsberg single-dish telescope corresponds to linear extensions of about 300 kpc at 8.35 GHz at the distances of the relics. The high degree of polarization indicates that the magnetic field vectors are almost perfectly aligned along the relic structure, as expected for shock fronts that are observed edge-on. The polarization degrees correspond to Mach numbers of >2.2. Polarized emission is also detected in the radio relics in ZwCl 0008+52 and, for the first time, in Abell 1612. The smaller sizes and lower degrees of polarizations of the latter relics indicate a weaker shock and/or an inclination between the relic and the sky plane. Abell 1612 shows a complex X-ray surface brightness distribution, indicating a recent major merger and supporting the classification of the radio emission as a radio relic. In our cluster sample, no wavelength-dependent Faraday depolarization is detected between 4.85 GHz and 8.35 GHz, except for one component of the Toothbrush relic. Faraday depolarization between 1.38 GHz and 8.35 GHz varies with distance from the center of the host cluster 1RXS 06+42, which can be explained by a decrease in electron density and/or in strength of a turbulent (or tangled) magnetic field. Faraday rotation measures show large-scale gradients along the relics, which cannot be explained by variations in the Milk...

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“…Model fitting and region selection of individual sources using BRATS is now a well established process [3,4,6,5,7]. Phase 1 of the surveys module will provide a method of automatically performing model fitting from a local database, with phase 2 expanding this capability to include the automated retrieval of complementary data using VO services.…”

Section: Discussionmentioning

confidence: 99%

“…The Broadband Radio Astronomy Tools software package (BRATS 1 ) already provides a range of tools for the analysis of radio sources and has successfully been applied to various source types including radio galaxies [3,4,5], cluster relics [6,7] and a non-thermal superbubble [8]. However, these studies have mainly been limited to well resolved, high fidelity, targeted observations where matched data are available over a wide frequency range, which is unlikely to be the case for both current and future surveys.…”

Section: Introductionmentioning

confidence: 99%

The systematic spectral analysis of radio surveys

Harwood¹,

Morganti²

2016

Proceedings of the Many Facets of Extragalactic Radio Surveys: Towards New Scientific Challenges — PoS(EXTRA-RADSUR2015)

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Current and future continuum surveys being undertaken by the new generation of radio telescopes are now poised to address many important science questions, ranging from the earliest galaxies, to the physics of nearby AGN, as well as potentially providing new and unexpected discoveries. However, how to efficiently analyse the large quantities of data collected by these studies in order to maximise their scientific output remains an open question. In these proceedings we present details of the surveys module for the Broadband Radio Astronomy Tools (BRATS) software package which will combine new observations with existing multi-frequency data in order to automatically analyse and select sources based on their spectrum. We show how these methods can been applied to investigate objects observed on a variety of spatial scales, and suggest a pathway for how this can be used in the wider context of surveys and large samples.

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A powerful double radio relic system discovered in PSZ1 G108.18-11.53: evidence for a shock with non-uniform Mach number?

Cited by 47 publications

References 63 publications

The GMRT 150 MHz all-sky radio survey

The GMRT 150 MHz all-sky radio survey

Relics in galaxy clusters at high radio frequencies

The systematic spectral analysis of radio surveys

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